Signaling circuits



June 24. 1924. 1,498,941

R. S. WILBUR SIGNALING CIRCUITS 5 Shgets-Sheet l File'd March 22. 1921 &

y wry June 24. 1924.

R. S. WILBUR SIGNALING CIRCUITS Filgq March 22 1921 5 Sheets-Sheet 2 AHQJune 24-, 1924. 1,498,941

R. S. WILBUR SIGNALING CIRCUITS Filed March 1921 s. WILBUR SIGNALINGClRCUITS Filed March 22. 1921 5 Sheets-Sheet 4 June 24 1924- R. S'WILBUR SIGNALING CIRCUITS 5 Sheets-Sheet 5 Filed March 22. 1921 SNQ //7v em for: flay 5. M/fiu/ atent June 24, 3924.,

S. WILBUR. F LYNDTIURST, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRICCOMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SIGNALING CIRCUITS.

Application filed March 22, 1921. Serial No. 454,556.

To all whom it may concern:

Be it known that I, RAY S. VVILBUR, a citizen of the United States,residing at Lyndhurst, in the county of Bergen and State of New Hersey,have invented certain new and useful Improvements in Signaling Circuits,of which the following is a full, clear, concise, and exact description.

This invention relates to signaling circuits and more particularly itrelates to telephone repeater circuits wherein repeater elements areemployed for amplifying telephone and other signaling currents.

As is well known in the art, a telephone repeater for two-way operationbetween two line sections preferabl comprises, when of the so-called22-type ,'a repeater element for repeating in each direction having its20 input terminals responsive only to currents in one line section. Theamplified currents from each repeater element are prevented from beingfed back on the input of the other repeater element by providing asuitable balancing artificial line and a threewinding transformer foreach line section and by connecting one winding of the threewindingtransformer to the line section. a second winding to itsartificial line,the input of one repeater element and the output of the other repeaterelemen being connected to the third winding an *the mid- -point of thefirst two windings respectively.

An object of this invention is to provide a suitable two-way repeater ofthe type above described together with the necessary auxiliary signalingapparatus which is particularly adapted to be used to interconnect oneline such as a submarine cable which may be permanentlyconnected to oneside of the repeater and a second line which may be one of several typesof land lines, for example, either associated with a. manual or anautomatic telephone system. A further object of the invention is toprovide a repeater circuit which may be connected at one endeither witha line having an individual network or wi th a line employing acompromise network in common with other lines of the same general type.Other objects will be apparent from the detailed description hereinaftergiven.

Briefly, the above objects are attained in the preferred embodiment ofthis invention by employing a three-winding transformer permanentlyconnected to the submarine cable and its balancing network and to theinput and output of the repeater elements, while the other side of therepeater elements, for use with a compromised balancing network isconnected to a second three-winding transformer and for use with linesemploying individual balancing networks is emplo ed a third three-Winding transformer. ne of the last three-winding transformers may, ifdesired, be normally in circuit with the submarine cable transformer andmeans may be provided for automatically disconnecting the same when itis desired to employ the other three-winding transformer.

Preferably, the operators' telephone set, the ringing apparatus andother auxiliary supervising apparatus. should be located electricallybetween the land line and its three-winding transformer so'that therepeater elements which are permanently connected to the submarine cablemay be employed for amplifying the signaling and talking currents ineither direction between the cable and'the repeater station. The

feature of having one of theland line threewinding transformers normallydisconnected from the repeater elements has made it preferable tocontrol the gain of the repeater elements by cutting in or outimpedances between the land, line and the three-winding transformerinstead of by the usual method of adjusting the input potentiometer ofeach repeater element. The adaptation of the repeater of this in ventionto use with land lines of several types has necessitated several novelsignaling and automatic switching features which will be hereinafterdescribed in detail.

The form of this invention described herein is particularly adapted tobe employed in connection with the voice frequency ringing systemdescribed in British Patent 179,006, to -Western Electric Company,Limited, filed February 22, 1921, wherein ,a double frequency oscillatoris disclosed.v

This invention will be better understood by reference to the'followingdetailed description taken in connection with the accompanying drawings,in which Figs. 1 and 2 when placed end to end illustrate the repeatersystem of this invention for interconnecting a submarine cable with landancing network by the double plu lines employing a compromise balancingartificial line; Figs. 1, 3 and 4 when placed end to end illustrate therepeater system of this invention for use in manual telephone systemsemploying an individual balancing network for each line; and Figs. 1, 3and 5 placed end to end illustrate the system for use with an automatictelephone system.

As explained above, the repeater clrcuits of this invention areparticularly adapted for the interconnection of a submarine cable with aland line for repeating telephone currents in either direction. Themanner in which th operator connects the circuits of the various figuresof this invention depend upon the type of land line to which aconnection is desired, for example, as to whether the land line is alocal subscribers line or a long distance toll line, or a line whichmust be obtained through an auto matic telephone exchange.

In case it is desired to connect to the submarine cable 10, of Fig. 1 alocal subscribers line, the single plug cord circuit of Fig. 2, isemployed by the operator putting plug 56 in jack 54 and by connectin thedesired local subscribers line to plug 4 of Fig. 2. If we assume thatplug 56 is in jack 54 and plug 74 is in the ack of the desired localsubscribers line; t e two-way transmission path for telephone currentsbetween the local subscribers line and the submarine cable may be tracedas follows: Incoming telephone currents from the submarine cable 10 bythe three-winding transformer 36, and filters 37 and 38, are impressedupon a suitable amplifier 39, and the amplified currents by transformer40 and leads 76 and 7.7 are impressed across the midpoints of a three-Winding transformer 78. Half of these incoming amplified currentswill beimpressed on the balancing artificial line 113 and the other half byconductors 79 and 80, jack 54, plug 56, ringing key 81, contacts ofsplitting key 83, conductors 84 and 85, ringing key 82 through plug 74to the local subscribers line. Speech currents from the localsubscribers line will travel over the same path from plug 74, throughthe threewindin transformer 78 where they, by the third winding 87 ofthe three-winding transformer, are impressed upon conductors 88' whichlead to a suitable amplifier 69 where telephone currents areamplifiedbefore being impressed through filters 89 and 90 upon themidpoints of three-winding transformer 36. If it is desired to connectthe submarine cable to a long distance line of a manual telephonesystem, the operator plugs the douleplug 59, and 60 of Fig. 3, intojacks 57 and 58 of Fig. 1, and connection is made to the long distanceline and its associated balfi 92 of Fig. 4," since as previouslyascribed Figs. 3 and 4 when placed end for end represent a double plugcord circuit for long distance manual lines. With such a connection, aswill be described later, the threewinding transformer 7 8 isautomatically disconnected and the incoming currents from the submarinecable which have been amplified by amplifier 39, are impressed by theconductors 93, jack 57, plug 59, conductors 94 upon the midpoints of athree-Winding transformer 95. Half of the incoming amplified signalswill be impressed through conductors 96 by suitable connections to theartificial line connected to the plug 92, while the other half, byconductors 98, will be impressed through the terminals of plug 91 uponthe long distance toll line. Incoming telephone currents from the lineconnected to plug 91 will be impressed upon the third winding 100 of thethree-winding transformer 95 and through plug 60, jack 58 and conductors88 upon the outgoing amplifier 69.

'- If, however, it is desired to connect the submarine cable to asubscribers line to which connection must be made through an automatictelephone exchange, the system is represented by Figs. 1, 3 and 5 placedend to end, double,plug 59, 60 being placed in jack 57, 58, whileconnection to the line of the automatic system and to its balancingnetwork is obtained through double plug 103 and 104. With such aconnection, the amplified currents from the submarine cable byconductors 93 are impressed upon the midpoints of a three-Windingtransformer 95 where they divide, half going to the artificial lineconnected to plug 104 and the other half going to the subscribers lineconnected to plug 103. Incoming speech currents from the line connectedto plug 103 by the third Winding 100 of the three-winding transformer 95are impressed through plug 60, jack 58 and conductors 88 to the outgoingamplifier 69.

When the single plug cord circuit of Fig. 2 is employed, it should benoted, as will appear from the detailed description hereinafter given,that a compromise network 113 is employed for balancing all the localsubscriber lines which may be connected to plug 74, and that at certaintimes in the operation of the re eater set the network 113 will beconnecte to the three-winding transformer 78 when there is no outgoingline connected to the other side of the transformer. In order to reventthe latter condition from causing t e two-way repeater to sing it hasbeen found necessary to insert padding elements 107 and 108 between theline plug 74 and the transformer 78, similar elements 109 and 110 beingplaced between the transformer 78 and the artificial line 113. Thesefour when artificialline 113 is connected to the transformer without theconnection of a correspondin real line. In one case where the gain ofthe repeater was'18 miles it was found that singing of the repeater didnot take place under the above conditions if each of these paddingelements introduced a 6 mile loss. \Vhen however. a real line wasconnected to plug 74 :1 tot ul loss of 6 miles instead of a 12 mile losswas suflicient to prevent singing.

Before beginning a detailed description of the operation of the repeatercircuits of this invention, it should be noted that relay 30 is normallyenergized over the following circuit: from ground. battery, winding ofrelay 30, conductor 31, left-hand contact. of relay 33, conductor 34,and the left-ham contact of relay 36 to ground.

Incoming voice frequency ringing currents from line 10 by three-windingtransformer 36, are impressed through filters 37 and 38 upon a suitableamplifier 39. which ma be of any well known type. The ampli ed ringingcurrents by transformers 40 and 41. are impressed upon a suitable voicefrequency ringing receiving system 42 which may be of the typedescribed, for example, in the British Patent 179,006 mentioned above.As described in that patent, the voice frequency ringing currents arecaused to break the holding circuit for a normally energized relaydesignated 44 in the applicants drawing. The breaking of this energizingcircuit for relay 44 due to incoming ringing currents, allows themovable contact of relay 44 to fall back and close the followingcircuit: ground, battery, contact of relay 44. conductor 46, right-handcontact of relay 33, conductor 48, winding of relay 49, conductor 50,and left-hand contact of normally energized relay 30 to ground.

The closing of this circuit by the release ofrelay 44, energizes relay49 which, by pulling up its left-hand contact locks up over thefollowing circuit: ground, battery, left-hand contact of relay 49,winding of relay 49, conductor 50. and the left-hand contact ofenergized relay 30 to ground. The closing of the right-hand contact ofrelay 49 closes the following circuit: ground, battery. right-handcontact of relay 49, conductor 50, left-hand contact of relay 36,signaling lamp 53 to ground.

The operator inresponding to the call may plug into jack 54. the plug 56of the single plug cord circuit shown in Fig. 2, or may plug into jacks57 and 58, the plugs 59 and 60 of the double plu cord circuit of Figs. 3and 4 or Figs. 3 an 5.

Operation of single plug cord. circuit of Fig. 2.

cut off the line lamp 53 by the closing of the following circuit:ground, battery, winding of relay 65, terminal 66 of plug 56, the sleeveof jack 54, and winding of relay 36 to ground.

The connection of plug 56 into jack 54 thereby causing the operation ofrelay 36 as above described, also causes the operation of relays 155 and156, by the closing of the following circuit over the contacts of relay36, grounded contact of relay 36, conductor 157, contact of ringingresponsive relay 158, conductor 159, and winding of relay 156 to batteryand ground. Relay 156 in operating operates relay 155 over the followingcircuit: ground, battery. winding of relay 155, contact of relay 156,conductor 157 and contact of relay 36 to ground. The function of relay155 will be described later. The 010'sing of this circuit also energizedrelay '65 which closes the following circuit: ground, battery, left handcontact of relay 65, conductor 145, winding of relay 146, contact ofringing responsive relay 147 .to ground, .thereby placing thesupervisory lamp 148 through conductor 149 and 150 in a well knownmanner under the control of the contacts of rela 's 146, 147 and 151.The energization o relay 36, asis evident from the drawing. extinguishesthe line lamp 53 since the energizing circuit therefor is cut off by thepulling up of the outer left-hand contact of relay 36. The energizationof relay 36 also breaks the holding circuit for relay 30 previouslytraced, from ground, battery, winding of relay 30, left-hand contact ofrelay 33,.the left-hand inner contact of relay 36 to ground. The fallingback of the left-hand contact of relay 30 may be employed for closing anenergizing circuit for the amplifiers of block .69 which are to beemployed for impressing outgoing amplified signals upon the submarinecable 10. For example, the ,connection of ground to lead 71 may beemployed for closin the circuit connections for a battery w ich may beused to energize the filaments of vacuum tube amplifiers to make themoperative. It is to be understood, however, that the outgoing'amplifier69 may be made operative in any other suitable manner by theenergization of relay 30.

The plugging in of plug 56 in the jack 54 also energizes relay 112 toconnect the compromise balancing network 113 to the three-windingtransformer 78 by the closing of the following path: ground, righthandcontact of relay 114, conductor 115, resistance 116, midpoint of retardcoil117,

conductors 118 and 119.,in parallel, con- T25 ductors 79 and 80 inparallel to the midpoint of retard coil 119 and thence through conductor120, winding of relay 121, and winding of relay 112 to battery andground. Relay 121 should preferably be a marginal relay so thatresistance 116 which is included in the circuit just traced, issuflicient to cut down the current. through the winding of relay 121 toprevent its operation while still allowing the operation of relay 112.The operation of relay 112 as is obvious from the drawing, energizesrelay 123 to connect the artificial network to the three? windingtransformer 78. The connection just traced between the midpoint ofretard coil 119 and the midpoint of retard coil 117 will hereinafter bedescribed simply as a simplex circuit.

The operator now operates the talking key 124 in order to connect theoperators set to the submarine cable to ascertain the connectiondesired. The operation of the talking key connects the operatorstelephone set to the real line side of the three-winding transformer 78by the following path: conductors 125. and conductors 118. 119 toconductors 79 and 80. The operation of the talking key also shuntsresistance 116 so that windings of relays 112 and 121 obtain groundthrough contact 128 instead of through resistance 116 to the groundedcontact of relay 114. This shunting of resistance 116 causes theoperation of relay 121 which. over a lead 129 by a circuit readilytraced. causes the operation of relays 130 and 131. to cut out one halfof the padding elements so as to increase the efi'ective transmissiongain of the repeaters while the operators telephone is in circuit.

Upon ascertaining the connection desired, the talking key is restored tonormal thereby deenergizing relay 121 so that the padding elements 108and 110 are again in circuit. The operator then plugs plug 74 into thejack of the line to which connection is desired. If the line to beconnected is one to which a battery should be connected. the jack 45should have its sleeve grounded through a resistance which, in the usualcase. is 50 ohms. The plugging in of plug 74 into jack 45. operatesrelays 47 and 68 over the following path from ground. resistance 43.jack 45. conductor 132. winding of relay 47.. conductor 133, and windingof relay 68 to battery and ground. The operation of relay 47 connectsthe line plug 74 to conductor 86 and disconnects from the line plug thebusy test lead 134 leading to the operators set. The auxiliary signalinglamp 135 is also lighted by the operation of relay 47 by the followingpath: ground, battery. left contact of relay 47 conductor 136, lamp 135.contact of relay 68, conductor 115 and contact of relay 114 to ground.

The operation of relay 68 connects the usmil condenser 138 to themidpoint of the primary winding of repeating coil 139. Relay 68 inoperating also operates relay 141) from ground. lower contact of relay68, winding of relay 140 to battery and ground.

The operation of relay 140, in pulling up its contacts. changes theconnection of condu tors 84. 85 and 86 previously interconnected byconductors 141 to interpose repeating coil 139 between conductors 84, 85and 86. The battery associated with relay 114 is connected to thesecondary winding of repeating coil 139 to supply current to theoutgoing line connected to jack 45.

The operator now rings the subscriber connected to line 101 by operatingringing key 82 which. in a well known manner. connects ringing currentbetween ground and lead 142 for calling the subscriber on line 101. Thecalled subscriber. in answering, as is usual in common battery systemsoperates relay 114 over the line 101 and the.

talking conductors to the line side of repeating coil 139 and winding ofrelay 114 to battery and ground. The operation of relay 114 allowsrelays 112 and 121 to get ground directly through lead 144 and energizedcontact of relay 114 instead of through resistance 116. This. aspreviously described. will cause the operation of relay 121 to cut outthe six mile padding elements 108 and 110.

If a disconnect signal comes over the cable 10, relay 44. as previouslydescribed. will release its contact to close the following circuit:ground. battery. contact of relay 44. conductors 46. 48. 50. outercontact of energized relay 36. left-hand inner contact of energizedrelay 155 to winding of relay 162 to ground. The operation of relay 162by the closing of this circuit connects a source of low frequencyringing currents. 16% cycles for example, to conductors leading to jack54' and disconnects jack 54'from conductors 79 and 80 which lead to thethree-winding transformer 78. The ringing currents pass over conductors7 9. 80. and 119, the contacts of the splitting key 83 and conductors164, 143 to the ringing responsive relay. 147, thereby causing theoperation of relay 147. The operation of relay 147 breaks the holdingcircuit for relay 146 previously traced, over contacts of relay 65, andthe deenergizationof relay 146. in a well known manner. causes theoperation of relay 151 to light the signal lam 148.

If it is desired to ring out on the sub-- marine cable, the ringing key81 is thrown, which connects a suitable source of ringing current to thering and tip conductors of plug 56 which, in passing over leads 79 and80 causes the o eration of ringing responsive relay 158 whic isconnected across the midpoints of the three-winding transformer 78. Theoperation of relay 158 breaks the energizing circuit of relay 156 whichhas been previously traced. The deenergization of relay 156 energizesrelay 165 by closing the following circuit: ground, batte winding ofrelay 165, right-hand contact 0 relay 166,

conductor 167, contact of deenergized relay 156, contact of energizedrelay 36 to ground. The operation ofrelay 165 causes the operation ofrelay 168 from ground. upper and outer contact of relay 165. winding ofrelay 168 to batteryand ground. The operation of relay 168 disconnectsthe outgoing conductors 88 from the third winding 87 of thethree-winding transformer 78 and connects them instead by conductors 179and inner contacts of relay 165 to a suitable source 161 of voicefrequency ringing currents. The voice frequency ringing currents fromsource 161 will then be impressed upon conductors 88, amplified byamplifier 69 and impressed upon the submarine cable.

If the source of currents 161 is a vacuum tube. oscillator deliveringtwo frequencies, the connecting of ground to lead 105 by the If at anytime it is desired to connect the submarine cable through the two-wayrepeater to a line in which battery is already resent, the jack of sucha line. such as ack 106 should have its sleeve grounded through a fairlylarge resistance such as 500 ohms. In such a case, relay 130 is operatedas in the condition when plug 74 was plugged in a jack with a 50 ohmsleeve, but the resistance of 500 ohms will prevent the operation ofrelay 131. Relay 131 being nonoperated, the

rlmary winding of relay 131 will be open-circuited" at the contact ofrela 131 and also relay 140 will not be operate The conductors 84 leadinto the threewinding transformer 78 will then be connected as shown inthe drawing throu h conductors 141, contacts of deenergize relay 140,conductors 85 and 86 through (plug 7 4 }to ition, t e g the outgoingline. In such a con battery connected to relay 114 will not be connectedto the outgoing line as in the previous case.

When the operator desires to monitor, the monitoring key 170 is operatedwhich, as is clear from the drawing, serves to connect the operator'stelephone set in shunt to the conductors between the three-windingtransformer 78 and the subscribers line connected to plug 74.

Operation of double plug co'rd circuit shown in Figs. 3 and 4.

If. instead of connecting the submarine cable to a local subscribersline, it is desired to connect the cable with a long distance toll lineof a manual telephone system, the double plug circuit of Figs. 3 and 4should preferably be employed. When lamp 53 is lighted in response toincoming signaling currents from the submarine cable 10, the double plug59 and 60, is connected into the double jack 57 and 58 of Fig. 1. Theinsertion of this double plug closes the following energizing circuit:from ground, windin of relay 170, the midpoint of retard coil 1 1,conductors 94 in arallel, conductors 93 in parallel to the midpoint ofthe secondary windin of transformer 40, conductor 173 and win ing ofrelay 33 to battery and ground. The above described connection inparallel of the conductors between the secondary of transformer 40 andretard coil 171 will hereinafter be described as a simplex circuit.

The closing of this circuit energizes relays 33 and 1 70. Relay. 33 inoperating, closes the following circuit: ground, inner lefthand contactof relay 33, conductors 174 and 175 to'winding of relay 166, battery andground, and through conductor 176, upper and outer contact ofdeenergized relay 165, winding of relay 168 to battery and ground. As iso vious from the drawing, the operation of relay 166 breaks theconnection between repeating coil 40 and the midpoint of three-windingtransformer 78, while the operation of relay 168 breaks the connectionsbetween the conductors 88 and the third winding of the transformer 78.The operation of this relay also opens the energizing circuit for relay30 previously traced through the left-hand outer contact of relay 33thereby deenergizing relay 30 and closing the circuit of the energizingbattery 7 O of the outgoin amplifier 69. The operation of relay 33 a soby its right outer contact breaks the short-circuit for the monitoringcoils 178, which, before the operation of relay 33 were short circuited'between points 179 and 180 {hrough the right-hand outer contact ofrehe-operation of relay 170 connectsground to lead 180 which leads tothe source of voice frequency ringing currents 182 and this rounding ofthe conductor may be employed to start the operation of the source ofringing currents by closing the filament. circuit for example of avacuum tube oscillator.

The operator thereupon operates the talking ke 181 of Fig. 4 whichconnects the operator s telephone set on the real line side of thethree-winding transformer 95 and at the same time by the contact beinmade at the point 182, a resistance 183 an a condenser 184 are connectedthrough the contacts of the splitting key 185 to the conductors 186 and96 which lead to the other side of the three-windin transformer 95. Thisnetwork 184 an 183 which is connected to that side of the three-windingtransformer 95 opposite the operators telephone set should have suchvalues as to maintain the electrical balance of the three-windingtransformer so as to prevent singing.

The operator on ascertaining the connection it is desired to make,connects the double plug 91, 92 into the jacks of the called toll line172 which we may assume is a line to which battery need not be suppliedand therefore the jack 191 has its sleeve connected to ground through aresistance of the order of 500 ohms. The placing of plug 91 into jack191 closes the followin circuit, ground, resistance 187, sleeve of ack191, winding of relay 187, conductor 188 and winding of relay 189 tobattery and ground. On account of resistance 187 being in this circuit,relay 189 will not be energized at this time but relay 187 will beenergized to connect the tip terminal of plug 91 to one of theconductors 190 which leads to the threewinding transformer 95. Relay 187by its right contact, connects battery and ground to winding of rela 192and contact of ringing responsive re ay 193 to ground. The aboveoperation enables ringing responsive rela 193, which is connected inshunt to the con uctors 190 and thereby responsive to ringing currentscoming in over the line connected to jack 191, to cause the operation ofrelays 192 and 193 in a well-known manner to control the signaling lamp194.

In case a disconnect signal should come in over the submarine cable,relay 44of Fig. 1 would be deenergized and would close the followingcircuit: from ground, contact of relay 44, conductors 46 and 47,right-hand inner contact of energized relay 33, conductor 192, midpointof the primary winding of transformer 194 over conductors 88 in parallelto the midpoint of the third winding 100, winding of relay 195,conductor 196, and conductor 197 to ground through a terminal of talkingkey 181. The operation of relay 195 closes the following circuit: fromground, right-hand contact of relay 195, conductor 198 to the signalinglamp 199 and then to battery and ground. Relay 195 at the same time islocked up from the grounded terminal of talking key 181, winding ofrelay 195, conductor 200, left-hand contact of energiz d relay 170 tobattery and ground. This locking circuit for relay 195, however, will beopened and the relay released as soon as the talking key 181 isoperated.

Ringing out over the submarine cable is accomplished by operating theringing key 201 which connects ground through its terminals, conductors202 and 203, winding of relay 204 to battery and ground, and conductor205, winding of relay 206 to battery and ground. The ground at key 201is also connected by lead 207 to the ringing oscillator 208 and thisconnection may be empl ed to start the generation of the two frzguenciesdesired. Relays 204 and 206,

.- meager are energized and relay 206, in operating, connects theoscillator 208 to the' leads 88 which allow the ringing currents fromthe oscillator to pass through amplifier 69 to the submarine cable.Leads 94 which serve to connect the output side of amplifier 39 to themidpoint's of the three-winding transformer 95 are disconnected from thethreewinding transformer by the energization o t' relay 204. It ispreferable to disconnect leads 94 from the midpoints of the threewindingtransformer 95 in order to preserve the balance of the three-windingtransformer, since relay 206 in operating disconnects the third winding100 from amplifier 69. The electrical balance can be maintained bydisconnecting the midpoints from the amplifier 39.

Rin mg over the subscribers line is accomplished by the operation ofringing key 210 which serves to connect leads from a suitable source ofringing current through conductors 212 to the outgoing line, at the sametime disconnecting from the outgoing line conductors 190 which lead tothe threewinding transformer 95. The operation of ringing key 210 putsground upon lead 213 thereby causing relay 214 to be energized so thatthe artificial line connected to plug 92 is disconnected from thethree-winding transformer 95 at the same time the outgoing line isdisconnected from the other side of the three-winding transformer, topreserve the electrical balance of the transformer.

If, however, connections are desired to a land line such as line 215 forwhich battery should be sup lied, the jack 216 connected thereto shouldhave its sleeve grounded through a resistance ofthe order of 60 ohms.The connection of plug 91 into jack 216 will then be sufficient to causethe energization of both relays 187 and 189 by a circuit previouslytraced in connection with jack 191. Relay 189, in operating,short-circuits the ringing responsive relay 193 and directly connectstogether the two sleeves of the primary winding of the repeating coil218. The operation of relay 189 by its lower inner contact, and byconductor 220 through the winding of relay 221 causes relay 221 to beenergized and connect the outgoing leads 211 to the secondary ofrepeating coil 218 instead of the former connection which was obtaineddirectly to conductors 190 without passing through the repeating coil.At the same time, relay 189 causes the operation of a relay 223 toconnect effectively in circuit a similar repeating coil 224 in theartificial line side of the three-winding transformer 95 so as tomaintain the electrical balance of the same.

The cutting in of the circuit of repeating coil 218 in a well knownmanner connects battery through the winding of relay 225 to the outgoingline. Relay 225 is therefore under control of the subscriber connectedto line 215 and by being deenergized or energized will light orextinguish the lamp 194 by means of a circuit traced from contact ofrelay 225, upper inner contact of relay 221, and lamp 194 to the rightcontact of rela 187.

henever monitoring is desired, the monitorin key 230 is thrown, whichconnects the telep one set in circuit with the monitoring coils 231 ofthe three-winding transformer 95by the conductors 232 which also leadthrough the terminals and234 of plugs 59 and 60 and conductors 236 tothe monitoring coils 17 8 of the three-winding transformer 36.

In case a variation is desired in the amount of amplification producedby the repeaters 39 and 69, the operator can increase v or decrease thesame by the'operation. of key 238. Key 238 when thrown in its firstposition connects ground through conductor 239 to operate relays 240 and241 to remove the padding elements 242 and 243 from the real line sideand the balancing network side of the three-winding transformer 95. Key238 in its second position will connect ground through lead 245 to energize relays for cutting out padding elements 246 and 247. The key inits other positions will remove still other padding elements, so thatany desired variation in the gain of the repeaters may be obtained.

peration of double plug 00rd circuits of F igs. 3 and 5.

line in an automatic telephone system.

When connection is desired to a line in such a telephone system, doubleplug 59, 60 is placed in double jack 57,58 and connection to the desiredline is made by double plug 103, 104.

The double plug cord circuit of Figs. 3 and 5 is adapted to be connectedwith either an automatic local subscribers line 240 directly, or to along distance toll line, such as 241, leading to a distant telephoneexchange. The operator, will, therefore, need to dial the number of thecalled subscriber only in case the double plug 103 and 104 is to beconnected to a local line, such as 240. In order to obtain a properoperation of the su aervisin and rm in 'a aratus the sleeve of eachlocal'line jack should be grounded through a high resistance which maybe 500 ohms, for example. while the sleeve of the jack for the longdistance toll line may be directly grounded.

If connection is desired to a local subscribers line, double plug 103,104 is placed in the double jack 242 and the following circuit is closedthereby: ground, resistance 243, sleeve of jack 242, conductor 244, andwinding of relay 245 to battery and ground. ltelay 245 is desired,however, not to operate on the closing of this connection to groundthrough a resistance of 500 ohms so that the plugging of plug 103 intojack 242 does not cause the operation of relay 245. In order to dial thenumber of the called subscriber, the operator throws the left-hand sideof splitting key 246 to close the following circuit: from ground, upperterminal of splitting key 246, conductor 247. winding of relay 248,contacts of dial 249 to battery and ground. Relay 248 in operating locksup over its lower contact to battery and ground and also energizes relay250 by closing the following path: from round and battery, right innercontact of relay 248, conductor 251, winding of relay 250 to ground. Theoperation of relay 250 connects dial 249 directly to the line terminalsof plug 103 so that the apparatus is now in position for the operator todial the desired number. Signaling to the called subscriber on line 240is accomplished by operating ringing key 252 which closes the followingcircuit from ground, contact of key 252, contact of deenergized relay245, conductor 254, winding of relay 255 to battery and ground. Theoperation of relay 255 grounds both sides of the line conductors 256which is a standard method of signaling a called subscriber. Relay 255in operating, also shortcircuits the conductors 257 which lead to thebalancing artificial line thereby maintaining the electrical balance ofthe three-winding transformer 105. Incoming signaling currentsfrom theline 240, as is usual in such systems, causes the operation of a relay260 bridgedacross conductors 256. Relay 260 in operating closes thecircuit to line lamp 261 which may be readily traced from the contact ofrelay 260,- left contact of relay 245 to lamp 261.

If, on the other hand. connection is desired to a long distance tollline, the double plug 103, 104 is insertedin the jack similar to jack263 which has its sleeve grounded through a low resistance. This, by acircuit previouslv traced. will cause the operation of relay 245. Relay245 in operating. closes the following circuit from ground. battery,left contact of relay 245. and winding of relay 265 to ground. Theenergization of relay 265 disconnects signal responsive-relay 260 fromacross the line conductors 256 and connects acrossinstead the ringingresponsive relay 266. At the same time relay 265 disconnects relay 260.italso removes retard coil 26? from across the artificial line conductor257 which is employed to balance retard coil 268 when relay 260 is incondition to be operated.

Ringing current is sent over the toll line 241 by the operation ofringing key 252 which connects ground through the righthand contact ofenergized relay 245, winding of relay 270 to battery and ground andthrough winding of relay 2T2, conductor 273, and the contact ofdecnergized relay 24-8 to battery and ground. Relay 272 in operatingconnects a suitable source of 16% cycle ringing current directly to theline terminals of plug 103 and at the same time disconnects the plugfrom the three-winding transformer 95. Relay 270 in operatingdisconnects the balancing network from the three-winding transformer 95in order to maintain the electrical balance of the system. Through thechain of relays 275, 276 and 266 incoming ringing currents are receivedto cause a suitable indication in a well-known manner by lamp 261.

It is to be understood that the specific form of this invention abovedescribed, may be variously modified without departing in any wise fromthe spirit of the invention as defined in the appended claims. Forexample, this invention is not limited in its use to repeater systemsfor submarine cables.

What is claimed is:

1. In an electric system, a repeater station comprisinga plurality ofrepeater elements, a line section terminating at said reppater stationand permanently connected no the input of one repeater element and theoutput of a second repeater element for two-way repeater operation, asecond line terminating at said repeater station, an artificial line forbalancing said second line, a \Vheatstone bridge network, one arm ofwhich comprises said second line, a second arm which comprises saidartificial line and means for completing the connections of the othertwo arms of the lVheatstone bridge through the respective output andinput terminals of the two mentioned repeater elements when repeateroperation is desired between said two lines.

2. In an electric system, a repeater station, a real line terminating atsaid station, an artificial line for balancing said real line, arepeater having input and output terminals, a second repeater havinginput and output terminals, said real line, artificial line, the inputterminals of said first repeater and the output terminals of said secondrepeater being permanently connected to form a balanced \Vheatsto'nebridge network, a second real line, an artificial line therefor, a threewinding transformer connected to said second line and said secondartificial line and adapted to be associated with the output terminalsof said first repeater and the input terminals of said second repeateran means for connecting said three winding transformer to said repeatmeaer from one of said lines to the other of saidlines. a second repeatingelement for repeating signals in the reverse direction, said repeaterstation when repeating between said lines comprising a three windingtransformer between each line and the two repeater elements, saidrepeater elements being normally connected to only one of said threewinding transformers.

ii. In an electric system, a two-way repeater station comprising aplurality of re peater elements and a plurality of three windingtransformers, said repeater elements being normally connected to one ofsaidthree winding transformers and means responsive to the connection ofsaid repeater elements to another of said three winding transformers forbreaking the connections from said repeater elements to the first threewinding transformer.

In an electric system, a repeater station comprising a repeater element,a plurality of three winding transformers, said repeater element beingnormally in circuit with one of said three winding transformers andmeans responsive to the connection of a second three winding transformerto said repeater element for disconnecting said repeater element fromthe first three winding transformer.

6. In an electric system, a repeater station comprising a repeaterelement, a three winding transformer for connecting said line to saidrepeater element, a second .three winding transformer, a second line,plug and jack means for connecting said three winding transformer tosaid repeater element and plug and iack means for connecting said secondthree winding transformer to said second line when repeating is desiredbetween said lines.

7. In an electric system, a repeater station, a plurality of linesterminating at said station, a plurality of repeater elements, athree-windingtransformer permanently connecting one of said lines tosaid repeater elements, a second three-winding transformer forconnecting the repeater terminals opposite said first line to a secondline and a third three-winding transformer for connecting the terminalsof said repeaters opposite said first line' to a third line.

8. In an electric system, a plurality of lines, a two-Way repeaterstation for interconnecting said lines and comprising repeater elements,a three-winding transformer at said station for each of said lines,means between one of said three-winding transformers and its associatedline for varying the effective gain of said repeater station, anartificial line for balancing said last mentioned line and connected tosaid three-winding transformer, and means for varying the impedance ofthe connections between said artificial line and said threewindingtransformer when the effective gain of said repeater station is varied.

9. In an electric system, a two-way re peater station, a linepermanently connected to one side of said repeater station, a pluralityof lines adapted to be connected to the other side of said repeaterstation, an artificial line for one of said real lines, a threewindingtransformer in said station adapted to be connected to one of said reallines and to said artificial line, and means for simultaneously varyingthe impedance between said three-winding transformer and said artificialline and between said three-winding transformer and the real linewhenever a variation is desired in the effective gain of said repeaterstation.

10. In an electric system, a two-way repeater station comprising athree-winding transformer, a line section connected to said transformeran artificial line for balancing said line section, a source of ringingcurrent,

means for disconnecting said line section from said three-windingtransformer and for connecting said source to said line section, andmeans responsive to said first means for disconnecting saidthree-winding transformer from said artificial line.

11. In an electric system, a line, a two- Way repeater stationcomprising a threewinding transformer having one winding in circuit withsaid line, a balancing network for said line in circuit with anotherwinding of said transformer, and means operating on an effectivevariation of the gain of said repeater to simultaneously vary theefiective impedance of the balancing network side of said transformer.

12. In an electric system, a plurality of lines, a repeater stationcomprising an amplifying repeating element adapted to repeat signalsfrom one of said lines to the other of said lines, a second amplifyingrepeating element for repeating signals in the reverse direction, saidrepeater station when repeating between said lines comprising balancedinductive coupling means between each line and the two repeater elementsfor insuring two-way repeater operation without singing, said repeaterelement being normally connected to only one of said coupling means.

13. In an electric system, two-way repeater station comprising aplurality of amplifying repeating elements, line terminals, balancedinductive coupling means for insuring two-way repeater operation betweensaid elements and one set of said line terminals, a second balancedinductive coupling peater,

means for insuring two-way repeater operation between said elements anda second set of said line terminals, said repeating elements beingnormally connected to one of said coupling means, and means responsiveto the connection of said repeating elements to said second couplingmeans for breaking the connection from said repeating elements to saidnormally connected coupling means.

ll. In an electric system, a plurality of lines, a two-way repeaterstation for inter connecting said lines and comprising ampli" fyingrepeating elements, balancing net-- works for said lines, inductivecoupling means for forming a balanced \Vheatstone bridge arrangementwith one of said lines, its balancing network, the input of one of saidelements and the output of'another of said elements, inductive couplingmeans for forming a balanced \Vheatstone bridge arrangement with anotherof said lines, its balancing network, the input of one of said elementsand the output of another of said elements, means between one of saidcoupling means and its associated line for varying the effective gain ofsaid repeater, and means for varying the impedance of the connectionsbetween the balancing network for said associated line and said couplingmeans when the effective gain of said repeater station is varied.

15. In an electric system, a repeater station comprising a two-wayamplifying repeater, a line section terminating at said station andpermanently connected to said repeater for two-way operation, a secondline terminating at said repeater station, an operators cord circuit,means for coupling said cord circuit to the side of said repeateroppositesaid first line, and means for coupling said cord circuit tosaid second line.

16. In an electric system, a repeater station comprising a two-wayamplifying repeater, a line section terminating at said stationandpermanently connected to said repeater for two-way operation, asecond line terminating at said repeater station, an operator's cordcircuit, means for coupling said cord circui't'to the side of saidrepeater opposite said first line, and means for coupling said cordcircuit to said second line,

said cord circuit comprising means for con-' trolling the application ofringing current to both of said lines.

17. In an electric system, a repeater station comprising a two-wayamplifying rea line section terminating at said station and permanentlyconnected to said repeater for two-way operation, a second line"terminating at said repeater station, an operators cord circuit, meansfor coupling said cord circuit to the side of saidrepeater opposite saidfirst line, and means for coupling said cord circuit to said secondline,.

said cord circuit comprising means for controlling the repeater gain fonone of said lines.

18. In an electric system, a repeater station com rising a two-wayamplifyin repeater, a ine section terminating at sai station andpermanently connected to said repeater for two-way operation, a secondline adapted to be connected to said repeater, said repeater comprisingan amplifying ele- 10 ment for amplifying signals from said first lineand comprising a second amplifying element for am lifying si nalsreceived from said second line, said rst amplifying element beingnormally operative, said second amplifying element being normallyinoperative and relay means under the control of the operator at saidstation folenergizing said second amplifying element.

In witness whereof, I hereunto subscribe my name this 19th day of MarchA. D., 1921.

RAY S. WILBUR.

